Re: C#/Java like interfaces for Nim

[Jehan]

Please note that `cast[...]` is an [unsafe 
operation](http://nim-lang.org/docs/manual.html#statements-and-expressions-type-casts)
 that literally reinterprets a bitpattern and does not care at all whether the 
underlying representations are in any way compatible. It is something that you 
want to avoid unless you specifically need the low-level functionality or 
require it for performance. It is recommended to use a normal type conversion 
instead.